Transmitters with carrier control are known, for example, from Meinke, Gundlach: Handbook of High Frequency Engineering, 1962, p. 1306, and also from U.S. Pat. No. 3,413,570. The advantage of amplitude modulated transmitters with carrier control is that, at low points of program modulation, that is, at a low modulation voltage, power can be saved so that the apparent "efficiency" of the transmitter is increased.
There are also known other techniques for increasing the efficiency of an amplitude modulated transmitter. For example, for modulation amplifier purposes, there can be used a switching amplifier for pulse duration modulated pulses, and which is followed by a filter section for filtering the switching frequency and which is preceded by a pulse duration modulator. With this arrangement, the pulse duration modulator converts modulation oscillation to pulse duration-modulated pulses which, upon amplification in the switching amplifier are re-converted by filter sections means, to an oscillation corresponding to the modulation oscillation. With such an arrangement, the improvement in transmitter efficiency is based on the high efficiency of the switching amplifier, such as shown in German Patent No. 1 218 557 and German Auslegeschrift No. 1 808 578. A further improvement in efficiency can be obtained by also having the driver operate as a switching amplifier with pulse duration modulated pulses, as shown in German Patent Application No. P 27 15 133.